1. Field of the Invention
The present invention relates to a fatigue safety factor testing apparatus and a method of testing a fatigue safety factor, and more particularly to a fatigue safety factor testing apparatus and a method of testing a fatigue safety factor which tests a fatigue safety factor dependent on temperature.
2. Description of the Related Art
A method of calculating a fatigue safety factor of a part using Computer Aided Engineering (hereinafter, to be referred to as “CAE”) is known. A calculation program for this purpose is commercially available in which a fatigue limit diagram is calculated to the part consisting of a kind of material under a predetermined condition, e.g., a predetermined temperature. Here, the fatigue limit diagram is a graph showing relationship between mean stress permissible to an object to be tested and permissible amplitude stress.
When only the fatigue limit diagram calculated under the predetermined condition can be used, it is difficult to accurately estimate an actual fatigue limit of the part in case of different conditions, e.g., different temperature depending on the location of the part. A component of an engine of a vehicle such as a piston is exemplified as such a part. In case of the piston, the piston moves in up and down directions in accordance with explosion in an engine cylinder at high speed, and the temperature is different largely depending on a portion of the piston.
Also, when the fatigue limit of the part can not be estimated precisely, it is not possible to estimate the fatigue safety factor of the part correctly. Therefore, the safety has the first priority and a very high safety factor is set. As a result, this leads the increase of weight of the engine, the increase of material cost and so on, resulting in increase of the environment load. Thus, the technique is demanded that can calculate the fatigue safety factor of each part at high speed and correctly through an automatic process based on the temperature and stress of every portion.
In conjunction with the above description, a processor for a numerical value simulation of a deformation process of a metal plate is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-339396). This conventional processor has an input section, a rapture limit distortion/wrinkle limit stress data storage section, a rapture/wrinkle margin calculating section, a rapture/wrinkle margin data storage section and an output section. The input section stores distortion/stress data of each element obtained from the numerical value simulation of a plastic deformation process of the metal plate using a finite-element method in the distortion/stress data storage section. The rapture limit distortion/wrinkle limit stress data storage section stores rapture limit distortion/wrinkle limit stress data. The rapture/wrinkle margin calculating section calculates a rapture/wrinkle margin of each element from the rapture limit distortion/wrinkle limit stress data and distortion/stress data of each element. The rapture/wrinkle margin data storage section stores the calculated rapture/wrinkle margin of each element. Then, the output section outputs a contour line distribution of the rapture/wrinkle margin.